Duplex lens



June 5, 1923.

A. w. POUGHER DUPLEX LENS Filed June 1. 1922 Patented June 5, 1923'.

U N i r ARTHUR, WILLIAM rouennn, or ivmncnnsrnn, ENGLAND.

DUPLEX Linus.

Applicationfiled June 1,

v Knut'sford Avenue, Upper Chorlton Road,

Manchester, I in the county of Lancashire, England, have invented a newand useful Improved Duplex Lens, of which the following is aspecification.

This invention relates to improved means for preventing dazzle: inconnection with the Q lamps of motor and other vehicles and has for itsobject an improved construction of lenses whereby the dazzle or glareis'el1m1 nated without reducing the light value.

According to the invention, I employ" a double or duplex lens,consisting of twodis tinct lenses, and each of the lenses is formed ofprisms of difl'erent diverging angles. The

lenses are suitably spaced apartand are lo cated in frontj of thesourcefoflight or the reflector. The rear lens, that is the lensnearestlthe source of light, and hereinafter referred to as thereceiving lens'splits up the lightrays projected from the source oflight, or from the reflector used in' conjunctiontherewith, whilst thefrontlens hereinafter'referred to as the projecting lens, acts tofurther break up the light rays received from the back lens. .1 I Theprismatic lenses are so ,arranged fthat the actual light rays or'beamsemitted from the front lens, or what may be termed the strong rays, iscontained within anangle of 20 degrees, whilst the light rays outsidethis angle consist of what may be termed weak or split up rays.Consequently when two vehicles approach one another from a distance thestrong rays of one vehicle will be visible to the other, but as thevehicles get closer together, each is cut off from the strong rays ofthe other, and thus neither suffers from the dazzling effect-of theothers lamps.

In order that the invention may be readily understood reference is madeto the accompanying drawings which show more or less diagrammaticallythe preferred method of carrying the same into effect.

Figure 1 is a sectional view of the two prismatic lenses as they wouldbe arranged in the lamp.

Figures 2 and 3 are diagrams showing the rays of light from the lamps oftwo appreaching vehicles, Figure 2 showing the 1922. Serial No. 5615325.

two vehicles some distance apart, andlig tire- 3 a similar'view when thevehicles are.

about to pass one another.

In Figure lithe back or indlcated atlA,;.thefront or nromctmglens at Band thesource of light which may ,con-

sist of a lamp proper ora reflector atC. 7

Each of the, lenses s of the plane-concave concave face of thelens -Abeing towards type with their concave faces outwardly, the}? c5receiving; lens is the source of lightand the concave face of the lens Bbeing towards'the illuminated I objective. The receiving lens A isbuiltupj of a series of symmetrical concentric-prisms, l Y

the centre prism D being of'greater vcross sectional area thanfthat ofthe prisms E, F," G, H and. the angular faces of the prlsms E to H areof successlvely greater length'and are struck from a common'base linelying, parallel with. the plane face'Kof thelens.

The faces of the centre prisms D asrepresented in Fig. 1 are at an angleof from 60 to 63 degrees with relation to the principal or central 'axisofthe lens, whilst-the faces or the prlsmsE to F are arranged at orabout 32 degrees from the principal or cenetral axis of the lens. withthe lamp C posi- I tioned substantiallv in. the relationship illustratedby Fig. 1, I find that, the'incident rays of-thep'rism D are convertedinto sub stantially. parallel emergent rays, whilst. the

incident rays of thev remaining'prisms, are

split up irregularly .ord-ilfused,

The front or projecting lens B has prism L the angular faces. of whichare 'ar-I rangedat an angle of about-65 to 66 degrees to the principalaxis of the lens, whilst the I i outermost prism M has its angular facearranged at an angle of'approximately 40 degrees to such axis, the facesof the interme. diate prisms .N N being all at or about 48 degrees. maybe frosted. The prisms L, M, N are all symmetrical and concentric, and Ifind that we by forming them'at the angles specified that thesubstantially parallel incident beams of The outer face of the prism fMlight of the central prism L from theprism D are converted intodivergent emerging beams, whilst the split up or irregular incidentbeams of the, prisms M,: N- are stillfurther split up, whereby the beamof light I emitted by the lamp outside the central beam from the prism Lis relatively weak.

The outer faces of thelenses may if de-Q ired'be plane surfaces insteadof concave,

but I prefer to employ lenses having the prisms forming a concavesurface so that the dark centre spot in lenses as at present constructedis eliminated.

Referring now to the diagrams shown in Figures 2 and 3, 0 represents theinner lamp of a vehicle travelling in the direction of the arrow 0 and Pthe lamp of an adjacent vehicle travelling in the direction of the arrowP As will be seen from the diagrams, either vehicle will only be withinthe angle of the strong rays indicated by the lines Q Q when saidvehicles are a comparatively long dis tance from the other, and as thevehiclesappreach one another as seen in the diagram inEigure 2 eachvehicle passes out of the range of the strong rays of the other somedistance before the moment of passing. The strong rays Q are confinedwithin an angle approximately degrees that is a cone of light rays isproduced having an angle of 10 degrees with its central axis. All lightrays -outside this cone of light constitute what may be termed weak orsplit up rays and are indicated by the sectioned lines at R R.

I claim 1. Means for preventing dazzle inlamps uin which a pair oflenses are employed, such lenses having prisms formed thereon,characterized in that the lenses are spaced apart and the prisms formedthereon comprise a plurality of concentric prisms the two innermost andopposite prisms being so shaped that raysof light passing therethroughfrom the source of light do not intersect and are emitted divergentlyfrom the prisms furthest from the source of light, whilst theremainprisms are so shaped that the rays of light emanating from thesource of light are directed from such latter prisms in such directionsthat they intersect and are diffused, whereby the light emitted from thelamp comprises two concentric beams of light, the

lens has its face located towards the objeetive formed of a plurality ofconcentric prisms, the two innermost and opposite prisms beingplano-convex and serving to emit non-intersecting rays of light, whilstthe remaining prisms are so shaped and 10-. cated as to direct the rays0t light emanatr ing from the source of light in such manner that theyintersect whereby they emit diffused light, so that the light emittedfrom the lamp comprises two concentric beams of light, the inner beingstronger than the outer tor the purpose specifier.

3. i l leans for preventing dazzle or glare in vehicle lamps, comprisinga rear lens having its face located towards a source of light formed ofa plurality of concentric and symmetrical prisms and its opposite faceplane, and a second lens located in front of the rear lens having itsface located towards the source of light formed plane and its oppositeface formed of concentricsymmetrical prisms, the prisms of one lensbeing of different diverging angle to the prisms of the other lens, thetwo innermost and 0pposite prisms being so shaped and located so as toemit a strong beam of non-diffused light,

whilst the remaining prisms are so shaped. and located as to emitdiffused light, where;

by the light emitted. from the lamp 'comprises two concentric beams oflight,- the in ner being stronger than the outer for the purposespecified.

ARTHUR WILLIAM POUGHER;

